Purchase Solution

Net charge on peptide

Not what you're looking for?

Ask Custom Question

Consider this peptide:

Phe-Glu-Ser-Met

What is the net charge of this peptide at ph=1
What is the net charge of this peptide at ph=7

Purchase this Solution
Solution Summary

The expert examines net charge on peptide for Phe-Glu-Ser-Met.

Solution Preview

To determine net charge on a peptide, you have to look at the pKa value for the different ionizing groups. That's the key.

In considering the structure of this peptide, we need to know what Phe-Glu-Ser-Met means. Peptides are always written with the N-terminal amino acid on the left side. Therefore, the structure is actually N-Phe-Glu-Ser-Met-C.

Knowing this, we can now list all of the ionizable groups in this tetrapeptide. I will use the pKa values on p. 113 of the second edition of Principles of Biochemistry (Lehninger, Nelson, Cox). If the values in your textbook are slightly different than these, that's okay. It shouldn't change the results too much.

N-Phe
There is no ionizable group in the R group in phenylalanine. Therefore, the only ionizable group we need to consider is the N-terminal group. Its pKa is 9.13. (Of course, the COOH group in phenylalanine doesn't exist in the peptide because it's involved in a peptide bond with glutamate.)

Glu
Both NH2 and COOH groups in glutamate don't exist because of the peptide bonds with phenylalanine ...

Purchase this Solution
Free BrainMass Quizzes
Biochemistry Basics

A refresher quiz to test your knowledge of basics concepts of biochemistry.

Parts of the Brain

This quiz will test your knowledge on different areas of the brain.

Hemophilia: Fact or Fiction

Do you know the truth about hemophilia? Test your knowledge here.

Vision and Oculomotor Control

This quiz will test the student's knowledge of the neural underpinnings of the visual system and its central pathways.

Pregnancy Knowledge

How much do you know about being pregnant? Test your Pregnancy IQ with this quiz!

View More Free Quizzes
Related BrainMass Solutions

  • Amino Acid Problems

    What's the total charge on this peptide at pH 2.0? We calculated it as 0 charge. Now we do Asp-Cys-Arg. What is the charge on Asp-Cys-Arg at pH 2.0? Since we already did Asp on the N-terminus, we know that is 0 net charge.

  • The net total charge of a protein

    18866 The net total charge of a protein What is the net total charge on the following protein at pH7 and at pH2? Two answers Lys-Glu-Phe-Lys This question is asking for the net change in protonation for the peptide from pH 7 to pH 2.

  • Biochemistry Questions: Ionization and Substrate Binding

    To calculate the net charge on the peptide at pH 6 we only need to add up all of the charges listed: (+1) + (+1) + (-2) = 0 ie. there is no net charge and this peptide is zwitterionic at pH 6.

  • Net Electrical Charge

    It doesn't affect the net electrical charge of the peptide. Tyrosine: The phenol's pKa is 10.1; therefore, we know that the OH group will be protonated, i.e. in this case, unionized as OH.

  • A Discussion On M/Z Of Trypsin-Digested Protein

    538052 A Discussion On M/Z Of Trypsin-Digested Protein You perform mass spectrometry on trypsin-digested peptides of 1g protein. a) One of the detected peptide ions has a +1 charge and an m/z ratio of 1267.78.

  • Determining mino acid sequences of peptide and octapeptide

    The N-terminus of T2 was valine The N-terminus of C3 was lysine At basic Ph the C3 fragment migrated with a net charge of +2 2.

  • Action of Trypsin on Peptides

    This will create fragments that have a charge based on whether their amino end (positive charge) is left open or carboxyl end is left open (negative charge) Electrophoresis separates proteins based on size and charge.

  • Determine the primary structure of the peptide

    Conclusion: If you're working on a question and you're beginning to think that the peptide just might be circular, you just might be correct! It determines the primary structure of the peptide. The solution is detailed and has a '5/5' rating.

  • Scissile Bond

    Bond C: This is a peptide bond, and it is the last peptide bond, i.e. the one at the carboxy-terminus of the peptide. Bond D: This is not a peptide bond. Bond E: This is not a peptide bond.

View More Related Solutions